Screw propeller



April 22, 1930. E, A, DEHMER 1,755,633

SCREW PROPELLER Filed Jin 24, 1929 AZTm-ney Patented Apr. 22, 1930 stars ERIK AUGUST DEHMER, OF STOCKHOLM, SWEDEN, ASSIGNO R TO CAPULATOR,-AKTIE- BOLAGET, F STOCKHOLM, SWEDEN, A CORPORATION OF SWEDEN softnw PROPELLER- Application filed July 24, 1929, Serial No. 380,633,.andin Sweden. and Germany August i, 1928.

This invention relates to'the construction" of a screw propeller having for its purpose to increase the useful eifect by reduction of the losses emanating from the usualchurning of the water. p p

The invention is illustrated in the accom-' panying drawing in which Fig. lshows the propeller seen from astern.

Fig. 2 is a diagrammatical projection of one 7 10 of the propeller blades on a spherical surface coinciding with thepressure surface of the blade, and s Fig. 3 shows the blade stretched flat. The direction of rotation of the propeller -IlS shown by arrows in the drawing (Figs. 1 and 2) and the blades having a curvature known in itself are at the leading edge provided with a cutting cam a or the like.

. The pressure surface of the blades coin- 2.0 cides in a known manner with an element of a sphere, and thus it is concave as .well in longitudinal as in transversal direction, as diagrammatically shown in Fig. 2.

If the root of the propeller blade is sup- I posed to stand on one of the great circles b of the sphere, so that a straight line 7) between the end pointsof theroot lies in the plane of I that great circle, then a line as from the middle of the line bto the tip of the blade, i. e. the end point having the greatest radius, counted in the direction of rotation will form a forward angle to a diametrical plane g through the middle of said line bin the sphere coinciding with the pressure surface of the blade, the centre of such sphere being designated 0 (Fig. 2). Further, if the pressure surface of the blade is assumed to be out by planes 0, d &c. parallel to the plane of the great circle, then the bases 0, d &c. of'the seg- 40 ments of the arcs of the blade surface so out are at angles to the base I) of the root segment and toeach other, these angles being greater the farther the section planes are from the plane of the great circle.

The root base 6 in the direction of rotation forms an obtuse angle with the propeller shaft, the axis of which is assumed to be positioned in the plane w (Fig. 2), and the bases 0, d &c. form corresponding angles with 60 the plane w, these angles being smaller the farther such bases are from the blade root or from the base Z). The element of the great What I claim and desire to secure by Letters Patent is I 5 Improvement in screw propellers having blades of common contour provided at the leading edge with a cutting cam and a presssure surface coinciding with an element of a sphere, such pressure surface being shaped in such a manner; that a base line of a cross section at the blade root coinciding with the great circle plane of the sphere forms an angle to the baselines of cross sections taken.

at a distance from and parallel with the great circle plane, such angle being greater the farther the section planes are from the plane of the great circle; and that a plane through the axis of the propeller shaft and the middle I of the blade root base line counted in the di- In testimony whereof I have signed name to this specification.

ERIK AUGUST DEI-IMER. 

